1. Field of the Invention
The present invention relates to a marine vessel which includes a propulsive force generating unit including an engine with an electric throttle as a drive source, and a marine vessel running controlling apparatus for such a marine vessel.
2. Description of the Related Art
An exemplary propulsion system provided in a marine vessel such as a cruiser or a boat for a leisure purpose is an outboard motor attached to a stern (transom) of the marine vessel. The outboard motor includes a propulsion unit provided outboard and including an engine as a drive source and a propeller as a propulsive force generating member, and a steering mechanism which horizontally turns the entire propulsion unit with respect to a hull of the marine vessel.
A control console for controlling the marine vessel is provided on the hull. The control console includes, for example, a steering operational section for performing a steering operation, and a throttle operational section for controlling the output of the outboard motor. The throttle operational section includes, for example, a throttle lever (remote control lever) to be operated forward and reverse by an operator of the marine vessel. The throttle lever is mechanically connected to a throttle of the engine of the outboard motor via a wire. Therefore, the output of the engine is controlled by operating the throttle lever. A relationship between the operation amount (operation position) of the throttle lever and the throttle opening degree is constant.
In a typical engine, a relationship between an engine speed and the throttle opening degree is nonlinear. In a lower throttle opening degree range of the typical engine, as shown in FIG. 29, the engine speed steeply increases with an increase in the throttle opening degree. In a higher throttle opening degree range of the engine, the engine speed moderately increases with the increase in the throttle opening degree.
Such a nonlinear characteristic significantly influences the control of a small-scale marine vessel including an outboard motor having no speed change gear. More specifically, as shown in FIG. 30, a resistance received by the marine vessel from a water surface varies in a complicated manner due to a frictional resistance and a wave-making resistance in the lower throttle opening degree range. In addition, the engine speed is steeply changed in response to a slight throttle operation, so that a propulsive force generated by the outboard motor is liable to be changed. When fine control of the propulsive force is required, for example, when the marine vessel is moved toward or away from a docking site, a higher level of marine vessel maneuvering skill is required. Therefore, an unskilled operator of a leisure boat or the like cannot easily control the throttle lever when moving the boat toward or away from a docking site.
In the automotive field, electric throttles have recently been used, which are driven by an actuator according an accelerator operation amount detected by a potentiometer. It is conceivable to use such an electric throttle for the engine output control of the propulsion system such as the outboard motor. In this case, the throttle lever operation amount-throttle opening degree characteristic, which is defined as a fixed linear relationship in the prior art arrangement having the throttle lever and the throttle mechanically connected to each other, can be flexibly modified. For example, the operation amount-throttle opening degree characteristic can be nonlinear. Therefore, the marine vessel maneuvering characteristic for lower speed traveling (with a lower throttle opening degree) for example, is improved by properly setting the operation amount-throttle opening degree characteristic.
The use of the electric throttle makes it possible to determine an operation amount-target throttle opening characteristic which provides a linear operation amount-engine speed characteristic, for example. However, the operation amount-target throttle opening characteristic does not necessarily satisfy an operator's demand. Where a large-size outboard motor is attached to a small-scale hull, for example, the engine speed is substantially changed according to the linear operation amount-engine speed characteristic when the throttle lever is operated from an idling state (throttle fully closed state). Therefore, it is desirable to modify the characteristic such that the throttle opening degree is slightly increased in response to a relatively great movement of the throttle lever. On the other hand, where a small-size outboard motor is attached to a large-scale hull, the throttle lever should be substantially moved for increasing the speed of the marine vessel over a hump range (a speed range in which a maximum wave-making resistance is observed). Therefore, it is desirable to modify the characteristic such that the throttle opening degree is significantly increased in response to a relatively small movement of the throttle lever.
Demands for the operation amount-engine speed characteristic vary depending on the types of the hull and the outboard motor as well as the purpose of the marine vessel and the level of the skill of the operator. With the use of the linear characteristic, it is difficult to satisfy the various demands. It is also difficult to prepare a multiplicity of characteristics for satisfying all of the demands.
If the operation amount-engine speed characteristic can be adjusted according to an operator's preference, it is possible to satisfy the individual operator's demands. For some of the operators unfamiliar with the control of the marine vessel, however, it is difficult to properly adjust many control parameters. Therefore, a more convenient way for adjusting the characteristic is desired.